The article
on mongabay.com deals about a proposed mechanism for generating carbon-negative
bioenergy. Bioenergy with carbon storage (BECS) holds out the prospect of
reducing CO2 from the atmosphere while producing carbon-negative energy. The
article provides an informative introduction on how "carbon-negativity" is
feasible and assumes geosequestration (developed from the "clean coal"
industry, CO2 capture in depleted oil and gas fields, saline aquifers etc.) as
the sequestering tool. Laurens Rademakers delineates the risks such as
deforestation of tropical rainforests and leakage of geosequestration. In
addition these technologies require vast capital inputs and large scale
projects.

Article about options to produce carbon negative energy, including biochar

Ancient skills "could reverse global warming"

Trials begin of a technique used by Amazon Indians that takes CO2 and locks it sfely into soil

Geosequestration
and carbon capture technologies are currently being developed by the coal industry
in order to produce the so-called "clean coal". Using this technology, the coal
industry can at best reduce its CO2 emissions, while using re-growing biomass
would establish a carbon sink. This substantive difference allows bio-energy
(energy from re-growing biomass) production systems to apply yet another way to
capture carbon - Charcoal Carbon Sequestration! Bio-energy with charcoal carbon
sequestration (BECCS) would only capture a maximum of 50% of the carbon stored
in the biomass but offers the following advantages:

Decentralized and small scale
projects are feasible

Large capital investments are
not necessary. The technologies range from small cooking stoves to large
bioenergy production units. No carbon capture technology is necessary as
charcoal is a byproduct of gasification. As price for the incomplete
gasification a proportion of the energy (geosequestration demands energy
too) is invested to capture carbon in charcoal.

Biochar (Charcoal used as soil
amendment) increases soil fertility and sustainability (important for
continuous cropping for energy or food crops)

No risk of harmful CO2 leakage
as in systems like geosequestration. Most scientists agree that the half
life of charcoal is in the range of centuries or millennia.

Only re-growing resources can
establish a carbon sink. Tropical Rainforest is not considered as
re-growing resource in a BECCS scenario. An access to the C trade market holds out
the prospect to reduce deforestation of primary forest, because using
intact primary forest would reduce the C credits. The estimated
above-ground biomass of unlogged forests is around 400 Mg ha‑1,
about half of which is C. This C is lost at a high percentage if used for gasification
and only < 50% is captured by BECCS. The C trade could provide an incentive
to cease further deforestation; instead reforestation and recuperation of
degraded land for fuel and food crops would gain magnitude.